(a) Field
Exemplary embodiments of the invention relate to a pixel circuit, a display device including the pixel circuit, and a method for driving the display device, and in particular, to a method for maintaining a voltage transmitted to a gate electrode of a driving transistor by effectively preventing an influence of a leakage current of a transistor.
(b) Description of the Related Art
Recently, various types of flat display devices, e.g., liquid crystal displays (“LCD”), field emission displays (“FED”), plasma display panels (“PDP”) and an organic light emitting diode (“OLED”) display, are widely used instead of cathode ray tubes (“CRT”) having relatively heavy weight and large size.
Among the various types of flat panel display devices, the OLED display including an OLED that generates light by recombination of electrons and holes to display an image typically has a fast response speed with low power consumption, and has high luminous efficiency, high luminance, and large viewing angle.
In general, a plurality of pixels in the OLED display includes an OLED for emitting light, and the OLED generates light of a predetermined luminance corresponding to a data current supplied from a pixel circuit.
Digital driving, which is one grayscale expression method of the OLED display, controls a turn-on time of a pixel. In the case of the OLED display using the digital driving method, a unit frame is divided into a plurality of sub-frames, and a light emitting period of each sub-frame is appropriately set to display a gray. The pixel emits light during a sub-frame selected based on an image signal for grayscale expression among the sub-frames constituting one unit frame. That is, the sub-frame selected based on the image signal is turned on to express the grayscale.
Each of the pixels generally includes the OLED, a driving transistor for controlling a current amount flowing to the OLED, a storage capacitor for charging a voltage that corresponds to a data signal, and a compensation circuit for compensating a threshold voltage of the driving transistor.
Such pixels charge a voltage that corresponds to the threshold voltage of the driving transistor and the data signal into the storage capacitor, and supply a current that corresponds to the charged voltage to the OLED to display predetermined images. However, the voltage transmitted to a gate electrode of a transistor for controlling light emission of the OLED may not be maintained substantially constant due to noise such as a leakage current or a ripple that may occur as a characteristic of the transistor.